Simple Circuit Experiments for Kids: Light a Bulb with One Battery and One Wire

Here’s a challenge that looks easy and isn’t: give a child one AA battery, one piece of wire and one small bulb, and ask them to light the bulb. Most try the obvious thing first, and it doesn’t work. That’s exactly why it’s a great lesson.

The challenge

You need:

One AA alkaline battery (1.5 V)
One piece of insulated wire, about 20 cm (8 in) long, with both ends stripped (a grown-up can strip them)
One small flashlight bulb rated for 1.5 V (a 2.5 V bulb also works but will glow more dimly)
Optional: bulb and battery holders, and a magnifying glass

The rule: keep trying until the bulb lights. Draw every setup that works and every one that doesn’t.

What to expect

Children will try the wire on top of the battery and the bulb on the wire, and nothing happens. Eventually someone discovers that the bulb has two contact points, the metal side and the metal tip at the bottom, and that both must touch the circuit, one to each end of the battery.

The setups that work all have something in common, and kids can see it in their drawings: there’s a complete loop from one end of the battery, through the bulb, back to the other end.

The science

Electricity needs a complete, unbroken path, called a circuit, to flow. The battery pushes electric charge around the loop. When the charge passes through the thin filament in the bulb, the filament heats up and glows. Break the loop anywhere and the flow stops.

A big mix-up is the idea that electricity travels from the battery to the bulb and is “used up.” In a circuit, charge flows around the loop, and the bulb transforms energy the charge carries into light and heat. The charge itself isn’t used up.

What lets electricity through?

Once the bulb lights, change the circuit and test everyday objects, such as a coin, a paper clip, a rubber band, a plastic spoon and a pencil. Predict first. Metals such as the paper clip and coin let the bulb light (conductors). Plastic, rubber and wood don’t (insulators). Pencil “lead” is graphite and does conduct, which usually surprises children.

The lesson What lets electricity through? turns this into a full investigation.

Why do some string lights all go out at once?

Many older strings of lights are wired in series: one single loop through all the bulbs. If one bulb is loose or burnt out, the loop is broken and the whole string goes dark. (Many newer strings have built-in workarounds, but the series idea is still the best way to understand why they were so annoying.)

Houses are wired in parallel: each light has its own branch, so one bulb failing doesn’t affect the rest.

Students can test this with two bulbs in one loop versus two in separate loops, unscrewing one bulb each time. Our lesson Why do some string lights all go out at once? does exactly that, and also compares brightness.

Safety

Use only AA or AAA batteries and small bulbs, never mains electricity or wall outlets.
A wire touching both battery ends without a bulb will get warm. Don’t leave it connected.
Keep button batteries away from small children.

More to try

Can you build a burglar alarm? uses a simple switch.
Try our free circuit lab to experiment with circuits on screen.

All of these lessons are in the Simple Circuits: Make It Light Up unit. Start with Can you light a bulb with one wire? and sign up for three lessons free.